1. Field of the Invention
The present invention relates to an optical pointing device, and more specifically, to an optical pointing device and control method thereof capable of preventing light from glaring out from an illumination unit when the optical pointing device is separated from working surface.
2. Description of the Related Art
An optical mouse is a peripheral input/output device of a computer that radiates light onto a surface across which it moves and receives light reflected from the surface to output movement information of the optical mouse. In general, the optical mouse is used on top of a flat working surface facing downward so that light radiated from the optical mouse is not directly visible to a user, but when the optical mouse is turned upside down, light output from the optical mouse is directly visible to the user and a glaring phenomenon may occur.
FIG. 1 is a block diagram of a conventional optical mouse, including a control unit 10, an input unit 20, and an illumination unit 30. The control unit 10 includes an image information output unit 11 including an image sensor 11-1 and a converter 11-2, a movement value calculation unit 12, and a communication unit 13. A lens of FIG. 1 refers to an optical structure that transmits light reflected from the working surface under the mouse to the image sensor. In addition, a dotted line of FIG. 1 indicates a direction in which light radiated from the illumination unit 30 is inputted to the image sensor 11-1.
A function of each block shown in FIG. 1 will be described below.
The control unit 10 detects an image on the working surface to calculate a movement value, receives signals from the input unit 20, and outputs of the calculated movement value and the input unit signals to an external device such as a computer.
The image information output unit 11 detects the image on the working surface and outputs image information on the detected image. The image sensor 11-1 receives light reflected from the working surface through the lens to detect image data and output an analog signal corresponding to the detected image data. The converter 11-2 converts the analog signal of the image sensor 11-1 into image information that is digital data and outputs the converted information.
The movement value calculation unit 12 calculates and outputs the movement value using the image information inputted from the converter 11-2 and outputs a control signal for controlling the illumination unit 30 in response to a state of the optical mouse 1 and a signal inputted from the communication unit 13.
The communication unit 13 receives signals corresponding to information inputted through the input unit 20 (e.g., an operation state of a button or a movement of a scroll device) and outputs the input unit signals and signals from an external device such as a computer to the movement value calculation unit 12, and outputs the movement information and the input unit signals to the external device such as a computer in response to the movement value inputted from the movement value calculation unit 12 and the input signal inputted from the input unit 20. The input unit 20, which may include buttons or scroll devices, outputs the input signal in response to manipulation by a user. The illumination unit 30 turns on or off in response to an illumination signal inputted from the movement value calculation unit 12 and radiates light onto the working surface when turned on. The illumination unit 30, which is used as a light source, may include a light emitting diode and a driving circuit to turn on or off the light emitting diode.
FIG. 2 is a state diagram for explaining operation of the conventional optical mouse shown in FIG. 1. Operation of the conventional optical mouse shown in FIG. 1 will be described below with reference to FIG. 2.
The conventional optical mouse has an active state in which the illumination unit 30 is turned on for most of the time and a movement value is calculated depending on the operation state of the optical mouse, an inactive state in which the light source is turned off for most of the time and turned on periodically to determine whether or not the optical mouse moves, and an idle state in which the light source remains in the off state.
As long as the optical mouse moves in the active state, it remains the active state (S1). However, when there is no movement of the optical mouse for a predetermined time in the active state, the optical mouse converts into the inactive state (S2). When there is no movement of the optical mouse in the inactive state, the optical mouse remains in the inactive state (S3). However, when movement of the optical mouse is detected, the optical mouse converts into the active state (S4). When there is no movement of the optical mouse for a predetermined time in the inactive state, the optical mouse converts into the idle state (S5). In the idle state, movement of the optical mouse is not detected, however when the input signal is generated by manipulation of the input unit, such as buttons, i.e., the input unit 20, the optical mouse converts into the active state (S6).
FIG. 3 is a diagram for explaining a method of controlling the illumination unit 30 in the conventional mouse shown in FIG. 1, in which FIGS. 3A and 3B show methods of controlling the illumination unit 30 in an active unit and in an inactive unit, respectively.
A method of controlling the illumination unit 30 in the conventional optical mouse will be described below with reference to FIG. 3.
In the active state (FIG. 3A), the illumination unit 30 turns on periodically with a predetermined first period T1. In the inactive state (FIG. 3B), the illumination unit 30 turns on periodically with a predetermined second period T2. The second period T2 is set to be longer than the first period T1.
In other words, the optical mouse calculates the movement value while turning the light source on relatively frequently in the active state (FIG. 3A), and determines whether or not the optical mouse moves while turning on the optical mouse relatively infrequently in the inactive state (FIG. 3B).
However, for the conventional optical mouse shown in FIG. 1, while the optical mouse is in the active state (FIG. 3A) or the inactive state (FIG. 3B), when the user turns the optical mouse upside down, light may glare out from the illumination unit 30. In addition, since the illumination unit 30 is unnecessarily turned on, power is unnecessarily consumed.
FIG. 4 is a block diagram of an embodiment of a conventional optical mouse with which the glaring phenomenon can be prevented, including a control unit 10, an input unit 20, an illumination unit 31, and a detection unit 40. The control unit 10 includes an information output unit 11 including an image sensor 11-1 and a converter 11-2, a movement value calculation unit 12, and a communication unit 13, and the detection unit 40 includes a sensor and a light emitting diode (LED). In FIG. 4, a dotted line indicates a direction in which light radiated from the illumination unit 31 is inputted to the image sensor 11-1.
A function of each block shown in FIG. 4 will be described below.
Functions of the control unit 10 and the input unit 20 are the same as described in FIG. 1.
The detection unit 40 radiates light using the light emitting diode (LED) and detects the light using the sensor to determine whether or not the optical mouse is separated from the working surface, and outputs a detection signal depending on the determination result. In other words, when the optical mouse is on the working surface, light radiated from the light emitting diode (LED) is reflected and detected with the sensor, and when the optical mouse is separated from the working surface, light radiated from the light emitting diode (LED) is not detected. Therefore, whether or not the optical mouse is separated from the working surface can be determined by whether or not light is detected with the sensor.
The illumination unit 31 turns on or off in response to the illumination signal inputted from the movement value calculation unit 12 of the control unit 10 and the detection signal inputted from the detection unit 40.
FIG. 5 is a block diagram for explaining operation of the illumination unit 31 of the conventional optical mouse shown in FIG. 4, including a resistor R1, a light emitting diode (LED), and two driving circuits DR1 and DR2 which may include a resistor R2 and a transistor TR1 and a resistor R3 and a transistor TR2, respectively.
A function and operation of each block shown in FIG. 5 is described below.
The driving circuits DR1 and DR2 turn on or off, respectively, in response to an illumination signal inputted from the movement value calculation unit 12 or a detection signal inputted from the sensor of the detection unit 40, to thus turn the light emitting diode (LED) on or off. The two driving circuits DR1 and DR2 are connected in series so that if one of them turns off, the light emitting diode (LED) turns off.
In other words, when the optical mouse is on the working surface, the sensor of the detection unit 40 outputs the detection signal with a high level, to thus turn on the driving circuit DR2. The light emitting diode LED then turns on or off in response to the illumination signal inputted from the movement value calculation unit 12. However, when the optical mouse is separated from the working surface, the sensor of the detection unit 40 outputs a detection signal with a low level, to thus turn off the driving circuit DR2. The light emitting diode (LED) then turns off, irrespective of operation of the movement value calculation unit 12.
However, for the conventional optical mouse shown in FIG. 4, if the optical mouse is turned upside down and light which is not radiated from the light emitting diode (LED) is inputted from the outside of the optical mouse to the sensor, it can be mistakenly determined that the optical mouse is on the working surface. In addition, since a separate light emitting diode (LED) is added to the detection unit 40 together with the illumination unit 31 for the control unit 10, power consumption is increased and extra parts are required. In addition, with two driving circuits as shown in FIG. 5, cost is further increased and a circuit is complicated.